大豆花叶病种子带毒及介体传播在流行中的作用

 大豆植株的生育时期,对大豆花叶病的发展程度和危害性,有明显的影响。单叶期最感病,抗性随着生育年龄的增长而提高,单叶期潜育期最短、发病率最高,危害性最大。开花、结荚期后感病,对植株生长影响不大,黑龙江省大豆田出现的蚜虫中,大豆蚜、桃蚜、玉米蚜、棉蚜均能传播SMV,蚜虫最早出现于6月上中旬,高蜂为7月中下旬,大豆花叶病田间传播主要发生在7月中旬以后,8月为传播盛期,观察圃病害传播初期,病株有明显的梯降分布。与对照区呈鲜明对比,说明除早期形成的病苗外,没有其他的自源侵染,病害传播距离不远,多数在5-15米内,少有超过25米的,垅间和逆风向传播距离更短,种子带毒形成的病苗,在流行中起主导作用。蚜虫传播发生晚,主要引起种子斑驳。

THE IMPORTANCE OF THE DISEASED SEEDLINGS FROM SMV INFECTED SEEDS AND THE VECTOR OF THE VIRUS IN THE EPIDEMIC

The development and severity of the soybean mosaic disease were gresatly related to the infection time in the developmental stage of the soybean plants.The primary leaf stage was the most susceptible.However,the resistance increased gradually as the plant developed.Susceptibility exhibited in short incubation period,high incidence and severe symptoms.Resistance increased obviously after flowering and podding stage.Among the various species of aphids found in soybean fields,Aphis glycine,Myzus persicae,Rhopaloslosiphum maidis and Eriosoma sp.transmitted SMV.The earliest appearance of aphids in the field was after early or mid-June.Two infection peaks were in mid-July and August.These were closely correlated with the vector spread of SMV which occurred about 15-20 days later.Infection gradients presented difinitely in six observation plots in contrast with the control plot.Excluding seed transmitted diseased seedlings,no other primary infection source was found.The distance of vector transmission was rather short that most of them occourred within 5-15 M from the infection source.For vector transmission happened very late,only mild symptoms including mottling seeds were resulted and the effect upon the growth was negligible,because the infection was in the time when host plants were in a state of maturing resistance.Seed transmission may be considered to play a critical role on epidemic of SMV under the circumstances in Heilongjiang province.